Technical Abstract:
In field trials established in 2004, different 3-yr potato cropping systems focused on specific crop management goals of (SC) soil conservation, (SI) soil improvement, and (DS) disease-suppression were evaluated for their effects on soilborne diseases and tuber yield. These systems were compared to (SQ) a typical 2-yr standard rotation and (PP) a non-rotation control, as well as under both rainfed and irrigated conditions. Previously, we reported on the effects after one full rotation cycle. Now, after 8 years and multiple seasons following two full rotation cycles, the DS system, which utilized Brassica and other disease-suppressive rotation crops, still maintained lower soilborne disease levels than all other rotations and high yields, whereas relative disease levels were higher and yield lower in the SQ system than previously observed. The SI system, characterized by yearly compost amendments, and irrigation, both resulted in higher yields, but also greater levels of black scurf and common scab. After several years of treatment, irrigated plots resulted in significant effects on disease and yield even in years when no irrigation was applied. Overall results indicate that over time, there were greater differences among the systems, with SQ demonstrating increased diseases and reduced yields relative to all the 3-yr systems. The DS system continues to perform well regarding maintenance of low disease levels and relatively high yields.